Injections of an inexpensive drug can halve the risk of life-threatening convulsions in pregnant women with a high blood pressure condition, an international study has found.

The three-year study looked at nearly 10,000 pregnant women with pre-eclampsia, a condition characterized by a sudden increase in blood pressure in late pregnancy.

Until now, the only sure way to prevent the seizures of full-blown eclampsia has been to induce early delivery of the baby.

The WHO estimates pre-eclampsia and eclampsia account for about 12 per cent of pregnancy-related deaths

The World Health Organization estimates pre-eclampsia and eclampsia occur in about three per cent of pregnant women and account for up to 60,000 pregnancy-related deaths worldwide.

Anticonvulsants, anti-epileptics and magnesium sulphate (Epsom salts) have all been used to prevent eclampsia but there was no conclusive evidence that they worked.

The WHO says this study, dubbed the Magpie trial, settles the issue of whether magnesium sulphate is the best approach to treating pre-eclampsia.

Women with pre-eclampsia may have risks of hypertension after their pregnancy

The clinical trial was co-ordinated by scientists at the Institute of Health Sciences in Oxford, England.

The results showed that women who received magnesium sulphate had a 58 per cent lower risk of eclampsia and a 45 per cent lower risk of dying than a control group who were given a placebo. It didn't help or hurt the babies' chance of survival.

The magnesium sulphate results were so good that the committee decided to stop the study early so all the women could receive the treatment.

The Magpie study appeared in the May 31 issue of the journal The Lancet.

Hypertension risks

In another recent study, researchers from the Magee-Womens Research Institute and the University of Pittsburgh School of Medicine found a link between pre-eclampsia and pre-term delivery.

They found blood concentrations of a metabolic sugar called sialic acid increased in women who develop pre-eclampsia with preterm delivery, but not term delivery.

Another study by researchers at the University of Pittsburgh found women with pre-eclampsia may continue to have a higher risk of hypertension and cardiovascular disease throughout their lives.

The studies were presented on June 3 at the 13th World Congress of the International Society for the Study of Hypertension in Pregnancy, in Toronto.